Aqueous Electrochemical and pH Studies of Redox-Active Guanidino Functionalized Aromatics for CO Capture.

Escalating levels of carbon dioxide (CO) in the atmosphere have motivated interest in CO capture and concentration from dilute streams. A guanidino-functionalized aromatic 1,4-bis(tetramethylguanidino)benzene (1,4-btmgb) was evaluated both as a redox-active sorbent and as a pH swing mediator for electrochemical CO capture and concentration. Spectroscopic and crystallographic studies demonstrate that 1,4-btmgb reacts with CO in water to form 1,4-btmgbH(HCO ).

Electrochemical Carbon Dioxide Capture and Concentration.

Electrochemical carbon capture and concentration (eCCC) offers a promising alternative to thermochemical processes as it circumvents the limitations of temperature-driven capture and release. This review will discuss a wide range of eCCC approaches, starting with the first examples reported in the 1960s and 1970s, then transitioning into more recent approaches and future outlooks. For each approach, the achievements in the field, current challenges, and opportunities for improvement will be described.

Davis-Beirut Reaction: A Photochemical Brønsted Acid Catalyzed Route to -Aryl 2-Indazoles.

The Davis-Beirut reaction provides access to 2-indazoles from aromatic nitro compounds. However, -aryl targets have been traditionally challenging to access due to competitive alternate reaction pathways. Previously, the key nitroso imine intermediate was generated under alkaline conditions, but as reported here, the photochemistry of -nitrobenzyl alcohols empowered Brønsted acid catalyzed conditions for accessing -aryl targets.

Accessing Multiple Classes of 2 H-Indazoles: Mechanistic Implications for the Cadogan and Davis-Beirut Reactions.

The Cadogan cyclization is a robust but harsh method for the synthesis of 2 H-indazoles, a valuable class of nitrogen heterocycles. Although nitrene generation by exhaustive deoxygenation is widely accepted as the operating mechanism in the reductive cyclization of nitroaromatics, non-nitrene pathways have only been theorized previously. Here, 2 H-indazole N-oxides were synthesized through an interrupted Cadogan/Davis-Beirut reaction and are presented as direct evidence of competent oxygenated intermediates; mechanistic implications for both reactions are discussed.

Photochemical Preparation of 1,2-Dihydro-3 H-indazol-3-ones in Aqueous Solvent at Room Temperature.

o-Nitrosobenzaldehyde is a reactive intermediate useful in the synthesis of nitrogen heterocycles. Previous strategies for using o-nitrosobenzaldehyde involve its isolation via chromatography and/or formation under harsh conditions. Herein, this intermediate was photochemically generated in situ from o-nitrobenzyl alcohols in a mild, efficient manner for the construction of 1,2-dihydro-3 H-indazol-3-ones using an aqueous solvent at room temperature.

N-N Bond Formation between Primary Amines and Nitrosos: Direct Synthesis of 2-Substituted Indazolones with Mechanistic Insights.

A concise, one-step route to indazolones from primary alkyl amines and o-nitrobenzyl alcohols is reported. The key step in this readily scalable indazolone forming process involves base-mediated in situ o-nitrobenzyl alcohol → o-nitrosobenzaldehyde conversion. Although this functional group interconversion is known to be useful for 2 H-indazole synthesis, its reactivity was modulated for indazolone formation.

Combination potentiator ('co-potentiator') therapy for CF caused by CFTR mutants, including N1303K, that are poorly responsive to single potentiators.

Background: Current modulator therapies for some cystic fibrosis-causing CFTR mutants, including N1303K, have limited efficacy. We provide evidence here to support combination potentiator (co-potentiator) therapy for mutant CFTRs that are poorly responsive to single potentiators.

Methods: Functional synergy screens done on N1303K and W1282X CFTR, in which small molecules were tested with VX-770, identified arylsulfonamide-pyrrolopyridine, phenoxy-benzimidazole and flavone co-potentiators.